转载于：https://www.modb.pro/db/69232
java常见的http请求库有HttpURLConnection、httpclient、RestTemplate、OKhttp，更高层次封装的 feign、retrofit
一、HttpURLConnection
HttpURLConnection 是 JDK 自带的标准库;
【优点】：不需要引入额外的依赖
【缺点】：缺乏连接池管理、域名机械控制等特性支持，在java9才支持 HTTP/2
public class HttpUrlConnectionDemo {
public static void main(String[] args) throws Exception {
String urlString = "https://httpbin.org/post";
String bodyString = "password=e10adc3949ba59abbe56e057f20f883e&username=test3";
URL url = new URL(urlString);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("POST");
conn.setDoOutput(true);
OutputStream os = conn.getOutputStream();
os.write(bodyString.getBytes("utf-8"));
os.flush();
os.close();
if (conn.getResponseCode() == HttpURLConnection.HTTP_OK) {
InputStream is = conn.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
StringBuilder sb = new StringBuilder();
String line;
while ((line = reader.readLine()) != null) {
sb.append(line);
}
System.out.println("rsp:" + sb.toString());
} else {
System.out.println("rsp code:" + conn.getResponseCode());
}
}
}
二、OkHttp
【优点】：OkHttp 接口设计友好，支持 HTTP/2，并且在弱网和无网环境下有自动检测和恢复机制，因此，是当前 Android APP 开发中使用最广泛的 HTTP clilent lib 之一。
当网络出现问题的时候 OkHttp 依然坚守自己的职责，它会自动恢复一般的连接问题，如果你的服务有多个IP地址，当第一个IP请求失败时，OkHttp 会交替尝试你配置的其他IP，OkHttp使用现代TLS技术(SNI, ALPN)初始化新的连接，当握手失败时会回退到TLS 1.0。
1、导入依赖
<dependency>
<groupId>com.squareup.okhttp3</groupId>
<artifactId>okhttp</artifactId>
<version>3.10.0</version>
</dependency>
2、简单使用
import okhttp3.*;
import org.apache.http.util.CharsetUtils;
import java.util.HashMap;
import java.util.Map;
public class OkHttpDemo {
OkHttpClient client = new OkHttpClient();
private String sendPostForm(String url, final Map<String, String> params) throws Exception {
FormBody.Builder builder = new FormBody.Builder(CharsetUtils.get("UTF-8"));
if (params != null) {
for (Map.Entry<String, String> entry: params.entrySet()) {
builder.add(entry.getKey(), entry.getValue());
}
}
RequestBody requestBody = builder.build();
Request request = new Request.Builder().url(url).post(requestBody).build();
return client.newCall(request).execute().body().string();
}
private String sendGet(String url) throws Exception {
Request request = new Request.Builder().url(url).build();
return client.newCall(request).execute().body().string();
}
public static void main(String[] args) throws Exception {
OkHttpDemo okHttpDemo = new OkHttpDemo();
String url = "https://httpbin.org/post";
params = new HashMap();
params.put("foo", "bar中文");
// Post请求
String rsp = okHttpDemo.sendPostForm(url, params);
System.out.println("http post rsp:" + rsp);
// Get请求
url = "https://httpbin.org/get";
System.out.println("http get rsp:" + okHttpDemo.sendGet(url));
}
}
3、项目应用
（1）配置文件
import okhttp3.ConnectionPool;
import okhttp3.OkHttpClient;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;
import java.security.KeyManagementException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.util.concurrent.TimeUnit;
@Configuration
public class OkHttpConfiguration {
@Bean
public OkHttpClient okHttpClient() {
return new OkHttpClient.Builder()
//.sslSocketFactory(sslSocketFactory(), x509TrustManager())
.retryOnConnectionFailure(false)
.connectionPool(pool())
.connectTimeout(30, TimeUnit.SECONDS)
.readTimeout(30, TimeUnit.SECONDS)
.writeTimeout(30,TimeUnit.SECONDS)
.build();
}
@Bean
public X509TrustManager x509TrustManager() {
return new X509TrustManager() {
@Override
public void checkClientTrusted(X509Certificate[] x509Certificates, String s) throws CertificateException {
}
@Override
public void checkServerTrusted(X509Certificate[] x509Certificates, String s) throws CertificateException {
}
@Override
public X509Certificate[] getAcceptedIssuers() {
return new X509Certificate[0];
}
};
}
@Bean
public SSLSocketFactory sslSocketFactory() {
try {
//信任任何链接
SSLContext sslContext = SSLContext.getInstance("TLS");
sslContext.init(null, new TrustManager[]{x509TrustManager()}, new SecureRandom());
return sslContext.getSocketFactory();
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (KeyManagementException e) {
e.printStackTrace();
}
return null;
}
/**
* Create a new connection pool with tuning parameters appropriate for a single-user application.
* The tuning parameters in this pool are subject to change in future OkHttp releases. Currently
*/
@Bean
public ConnectionPool pool() {
return new ConnectionPool(200, 5, TimeUnit.MINUTES);
}
}
（2）utils 工具类
import okhttp3.*;
import org.apache.commons.lang3.exception.ExceptionUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.File;
import java.util.Iterator;
import java.util.Map;
public class OkHttpUtil{
private static final Logger logger = LoggerFactory.getLogger(OkHttpUtil.class);
private static OkHttpClient okHttpClient;
@Autowired
public OkHttpUtil(OkHttpClient okHttpClient) {
OkHttpUtil.okHttpClient= okHttpClient;
}
/**
* get
* @param url 请求的url
* @param queries 请求的参数，在浏览器？后面的数据，没有可以传null
* @return
*/
public static String get(String url, Map<String, String> queries) {
String responseBody = "";
StringBuffer sb = new StringBuffer(url);
if (queries != null && queries.keySet().size() > 0) {
boolean firstFlag = true;
Iterator iterator = queries.entrySet().iterator();
while (iterator.hasNext()) {
Map.Entry entry = (Map.Entry<String, String>) iterator.next();
if (firstFlag) {
sb.append("?" + entry.getKey() + "=" + entry.getValue());
firstFlag = false;
} else {
sb.append("&" + entry.getKey() + "=" + entry.getValue());
}
}
}
Request request = new Request.Builder()
.url(sb.toString())
.build();
Response response = null;
try {
response = okHttpClient.newCall(request).execute();
int status = response.code();
if (response.isSuccessful()) {
return response.body().string();
}
} catch (Exception e) {
logger.error("okhttp3 put error >> ex = {}", ExceptionUtils.getStackTrace(e));
} finally {
if (response != null) {
response.close();
}
}
return responseBody;
}
/**
* post
*
* @param url 请求的url
* @param params post form 提交的参数
* @return
*/
public static String post(String url, Map<String, String> params) {
String responseBody = "";
FormBody.Builder builder = new FormBody.Builder();
//添加参数
if (params != null && params.keySet().size() > 0) {
for (String key : params.keySet()) {
builder.add(key, params.get(key));
}
}
Request request = new Request.Builder()
.url(url)
.post(builder.build())
.build();
Response response = null;
try {
response = okHttpClient.newCall(request).execute();
int status = response.code();
if (response.isSuccessful()) {
return response.body().string();
}
} catch (Exception e) {
logger.error("okhttp3 post error >> ex = {}", ExceptionUtils.getStackTrace(e));
} finally {
if (response != null) {
response.close();
}
}
return responseBody;
}
/**
* get
* @param url 请求的url
* @param queries 请求的参数，在浏览器？后面的数据，没有可以传null
* @return
*/
public static String getForHeader(String url, Map<String, String> queries) {
String responseBody = "";
StringBuffer sb = new StringBuffer(url);
if (queries != null && queries.keySet().size() > 0) {
boolean firstFlag = true;
Iterator iterator = queries.entrySet().iterator();
while (iterator.hasNext()) {
Map.Entry entry = (Map.Entry<String, String>) iterator.next();
if (firstFlag) {
sb.append("?" + entry.getKey() + "=" + entry.getValue());
firstFlag = false;
} else {
sb.append("&" + entry.getKey() + "=" + entry.getValue());
}
}
}
Request request = new Request.Builder()
.addHeader("key", "value")
.url(sb.toString())
.build();
Response response = null;
try {
response = okHttpClient.newCall(request).execute();
int status = response.code();
if (response.isSuccessful()) {
return response.body().string();
}
} catch (Exception e) {
logger.error("okhttp3 put error >> ex = {}", ExceptionUtils.getStackTrace(e));
} finally {
if (response != null) {
response.close();
}
}
return responseBody;
}
/**
* Post请求发送JSON数据....{"name":"zhangsan","pwd":"123456"}
* 参数一：请求Url
* 参数二：请求的JSON
* 参数三：请求回调
*/
public static String postJsonParams(String url, String jsonParams) {
String responseBody = "";
RequestBody requestBody = RequestBody.create(MediaType.parse("application/json; charset=utf-8"), jsonParams);
Request request = new Request.Builder()
.url(url)
.post(requestBody)
.build();
Response response = null;
try {
response = okHttpClient.newCall(request).execute();
int status = response.code();
if (response.isSuccessful()) {
return response.body().string();
}
} catch (Exception e) {
logger.error("okhttp3 post error >> ex = {}", ExceptionUtils.getStackTrace(e));
} finally {
if (response != null) {
response.close();
}
}
return responseBody;
}
/**
* Post请求发送xml数据....
* 参数一：请求Url
* 参数二：请求的xmlString
* 参数三：请求回调
*/
public static String postXmlParams(String url, String xml) {
String responseBody = "";
RequestBody requestBody = RequestBody.create(MediaType.parse("application/xml; charset=utf-8"), xml);
Request request = new Request.Builder()
.url(url)
.post(requestBody)
.build();
Response response = null;
try {
response = okHttpClient.newCall(request).execute();
int status = response.code();
if (response.isSuccessful()) {
return response.body().string();
}
} catch (Exception e) {
logger.error("okhttp3 post error >> ex = {}", ExceptionUtils.getStackTrace(e));
} finally {
if (response != null) {
response.close();
}
}
return responseBody;
}
}
三、RestTemplate
RestTemplate： 是 Spring 提供的用于访问Rest服务的客户端， RestTemplate 提供了多种便捷访问远程Http服务的方法，能够大大提高客户端的编写效率。
1、导入依赖
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
2、关于注入RestTemplate对象
RestTemplate 在源码中是没有@Bean注入的，因此，我们不能直接使用如下方式直接注入
@Autowired
private RestTemplate restTemplate;
【解决方案】
（1）方式一：如果要使用，可以编写配置文件自己注入
@Configuration
public class ApiConfig {
@Bean
public RestTemplate restTemplate(ClientHttpRequestFactory factory) {
return new RestTemplate(factory);
}
@Bean
public ClientHttpRequestFactory simpleClientHttpRequestFactory() {
//默认的是JDK提供http连接，需要的话可以//通过setRequestFactory方法替换为例如Apache HttpComponents、Netty或//OkHttp等其它HTTP library。
SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
factory.setReadTimeout(5000);//单位为ms
factory.setConnectTimeout(5000);//单位为ms
return factory;
}
}
（2）也可以通过自己新建对象直接使用
RestTemplate restTemplate = new RestTemplate();
3、如何使用
（1）Get 请求
// 方式一
Notice notice = restTemplate.getForObject("http://fantj.top/notice/list/{1}/{2}", Notice.class,1,5);
// 方式二
Map<String,String> map = new HashMap();
map.put("start","1");
map.put("page","5");
Notice notice = restTemplate.getForObject("http://fantj.top/notice/list/", Notice.class,map);
（2）Post 请求
// 方式一
String url = "http://demo/api/book/";
HttpHeaders headers = new HttpHeaders();
MediaType type = MediaType.parseMediaType("application/json; charset=UTF-8");
headers.setContentType(type);
String requestJson = "{...}";
HttpEntity<String> entity = new HttpEntity<String>(requestJson,headers);
String result = restTemplate.postForObject(url, entity, String.class);
System.out.println(result);
// 方式二
String url = "http://47.xxx.xxx.96/register/checkEmail";
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
MultiValueMap<String, String> map= new LinkedMultiValueMap<>();
map.add("email", "844072586@qq.com");
HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<>(map, headers);
ResponseEntity<String> response = restTemplate.postForEntity( url, request , String.class );
System.out.println(response.getBody());
四、Feign/OpenFeign
可以看这篇：Spring Cloud OpenFeign详解 —— https://blog.csdn.net/taiyangdao/article/details/81359394